Glass, both transparent and translucent, has been used as glazing material for windows and partitions and, for certain uses, it is painted or stained to provide specific decorative effects. Glass is high in density and weight, is difficult to fabricate at the work site, is generally brittle, and can constitute a safety hazard.
Glass substitutes such as polyvinyl chloride sheeting, acrylic, e.g., poly(methyl methacrylate), sheeting and polycarbonate sheeting have been used as substitutes for glass in certain glazing applications. Generally, these substitutes are made for clear (transparent), non-decorative applications. The sheet material provided by this invention may be used primarily for producing or obtaining decorative applications with varying degrees of transparency and various levels of enhanced security.
Articles made from copolyester sheet are described in U.S. Pat. Nos. 5,894,04, 5,958,539, 5,998,028, 5,643,666, and 6,025,069. However, applications exist whereby higher creep/thermal resistances compared to neat copolyester are needed, for instance backlit paneling. In addition, replacing neat copolyester with neat polycarbonate is undesirable as well, since polycarbonate has to be dried prior to composite fabrication thereby increasing cycle time and cost. Polycarbonate also must be laminated at high temperatures, which can cause degradation of the decorative layer. Further, polycarbonate is difficult to post-form without pre-drying and requires higher forming temperatures.
U.S. Pat. No. 5,413,870 describes a sturdy wall covering especially useful in a bathroom or shower area, the wall covering being comprised of a laminate that includes a clear or transparent acrylic cast in the first layer, a clear polyester thermoset resin in the second layer, and a thin fabric sheet as the third layer and a pigmented polyester thermoset coating over the fabric layer. The polyester thermosetting resins in this case are applied as a liquid and subsequently cured as a solid. There are several difficulties when using polyester thermosetting resins. Removing air bubbles from the liquid thermosetting resins can be difficult. Thermosetting resins can undergo significant shrinkage during curing. In addition, crosslinked polyester resins are known to be brittle. This invention alleviates many of these difficulties.
Advantages of this invention over the prior art include higher heat deflection temperature (HDT), increased stiffness and increased creep resistance with time.